Field of the invention.: In ground fabricated rigid pools and structures, which are located in expansive clay type soil.
Description of the prior art.: A rigid pool or structure which is fabricated in ground, the soil of which is comprised of expansive clay type, has to have the area over excavated well beyond the outside surfaces of the walls and floors, the structure formed and poured in place, and the over excavated area backfilled with non-expansive soil.